1,721,028 research outputs found
Towards the sustainability of nuclear energy: analytical approaches for the solution of the fuel equilibrium vector and application to an adiabatic lead fast reactor
No full textA possible strategy for the long-term sustainability of nuclear energy is to use fast reactors with closed fuel cycles, i.e. to recover all the actinides in the spent fuel (including the MA, Minor Actinides) and recycle them in the reactor itself. In this way the fuel cycle can have as input only depleted (or natural) Uranium and as final waste only the fission products and the losses in the fuel reprocessing (e.g. 0.1%). The feasibility of this approach depends on the equilibrium fuel configuration (the fuel composition attained after infinite cycles), when the final isotopic composition of the fuel after a certain irradiation time t1 and cooling time t2 turns out to be exactly the same as the one which has been loaded (except for Uranium). Two independent mathematical methods are here outlined for the solution of the fuel equilibrium composition. These methods are then validated by the codes FISPACT and MCNPX and applied to the European lead fast reactor ELSY. The fraction (on the total actinides) at equilibrium turns out to be in this case 0.9% for the MA and 17.2% for the Pu. The keff and the βeff are then calculated showing the promising features of this approach
Study of isotopes production for the SPES project
No full textThe Monte Carlo calculations for the isotopes production in the UCx target (SPES project) are considered. The fragments are generated from the fission of 238U, using fast neutrons coming from a converter target (two target scheme). The neutron production yields from the converter target, as well as the energy and angular distributions from different material targets have been investigated. In all simulations, using the MCNPX code, we refer to a proton primary beam at 100 MeV energy, 1 mA, 100 kW power on the converter. The number of fissions (about 1013 fissions/s) and the production rates of neutron-rich nuclei were calculated for different converter materials
PDS-XADS: Radiation Transport Responses in the Windowless Target
No full textThis document was prepared in the framework of PDS-XADS (Preliminary Design Studies of an eXperimental Accelerator Driven System) as a contribution to Deliverable 60.1, Work Package 4.3, which analyses the characteristics of different target options. Here some features of the windowless Lead-Bismuth target (coupled with a Lead-Bismuth cooled core) are investigated by means of the Monte Carlo computer code MCNPX: the neutron yield (14.5 neutrons/proton), the formation of the spallation products, the heat deposition (at BOL l.3MW are deposited in the whole target coolant), the different contributions to the neutron flux (the maximum value at BOL is 3.7E15 n cm-2 sec-1 and in the central zone of the target the contribution from the core varies radially from 23% to 90%) and the proton flux (which decreases linearly as the protons penetrate into the target)
A new paradigm for core design aimed at the sustainability of nuclear energy: The solution of the extended equilibrium state
No full textThe future expansion of nuclear energy, a technology identified as one of the main candidates for reducing the world's dependence on fossil fuels, requires a thorough analysis of the sustainability of this energy source for long-term supply. Generation-IV nuclear systems could represent a turning point for energy production by minimizing the environmental footprint of the fuel cycle. A new paradigm is thus required for reactor design, focusing, at the core design level, on both the closure of the fuel cycle and the effective utilization of natural resources. Within this framework, the so-called 'adiabatic core' concept represents a particularly interesting solution. It is based on the idea of achieving by design a condition of equilibrium in the fuel cycle (i.e., an equilibrium 'fuel vector'), foreseeing nuclear power systems able to maintain a constant total amount of both plutonium and minor actinides (TRU), consuming only uranium (either natural or depleted), while discharging to the environment only fission products and reprocessing losses. Under such a hypothesis, all actinides can be continuously recycled in the same system, reducing both the waste volume and its long-term radiotoxicity, as well as utilizing effectively uranium resources. Two mathematical approaches have been devised to find the 'extended' equilibrium solution for the fuel vector. These methods are compared, validated with the codes MCNPX and FISPACT and applied to the European lead-cooled fast reactor ELSY, confirming the potential of this approach (e.g., a reduction by two orders of magnitude of the TRU mass in the final waste in comparison with the fuel cycle of Light Water Reactors operated in a once-through scenario)
In-phantom imaging of all dose components in boron neutron capture therapy by means of gel dosimeters
No full textThe experimental method for in-phantom imaging and profiling the absorbed dose in neutron capture therapy has been improved. The method separates the contributions of the various secondary radiation components and is based on suitably designed gel dosimeters in the form of layers. The discrimination of the dose components is achieved by means of pixel-to-pixel manipulations of images obtained with gel dosimeters having different isotopic composition. Large dose images are obtainable with this method, because the layer geometry of dosimeters avoids sensible variation of neutron transport due to the isotopic composition of gel. Operation modalities aimed at attaining more reliable results have been studied. Some results, together with the results of punctual measurements performed with conventional dosimeters and with MC calculations, are here reported
EFIT - Power Deposition Distribution and Neutron Source Calculations by Means of MCNPX
No full textThis document was prepared as a contribution to Deliverable 1.6 in the framework of the EFIT project:the Euuropean Facility for Industrial Transmutation (VI Framework Program, EUROTRANS). This is a conceptual design for transmuting minor actinides in ADS (Accelerator Driven Systems). The proton beam ha an energy of 800 MeV and impinges on a lead target, providing the neutron source for the sub-critical system. Lead is also the coolant far the 384 MWth core. The U-free core has been designed by means of the deterministic code ERANOS, while here some neutronic features are investigated by means of the Monte Carlo code MCNPX: the neutron source, the keff, the ks, the proton current, the power deposition distribution in the target and in the core (power peaks and axial form factors). These latter results are passed to FZK and will be used as inputs for the thermohydraulic analyses. All these quantities have been evaluated at Beginning of Cycle
The RIB production target for the SPES project
No full textFacilities making use of the Isotope Separator On-Line (ISOL) method for the production of Radioactive Ion Beams (RIB) attract interest because they can be used for nuclear structure and reaction studies, astrophysics research and interdisciplinary applications. The ISOL technique is based on the fast release of the nuclear reaction products from the chosen target material together with their ionization into short-lived nuclei beams. Within this context, the SPES (Selective Production of Exotic Species) facility is now under construction in Italy at INFN-LNL (Istituto Nazionale di Fisica Nucleare — Laboratori Nazionali di Legnaro). The SPES facility will produce RIBs mainly from n-rich isotopes obtained by a 40 MeV cyclotron proton beam (200 μA) directly impinging on a uranium carbide multi-foil fission target. The aim of this work is to describe and update, from a comprehensive point of view, the most important results obtained by the analysis of the on-line behavior of the SPES production target assembly. In particular an improved target configuration has been studied by comparing different codes and physics models: the thermal analyses and the isotope production are re-evaluated. Then some consequent radioprotection aspects, which are essential for the installation and operation of the facility, are presented. © 2015, SIF, Springer-Verlag Berlin Heidelberg
PDS-XADS: Spallation Neutron Source
No full textThis document was prepared in the framework of PDS-XADS (Preliminary Design Studies of an eXperimental Accelerator Driven System), as contribution to Deliverable 49 (Work Package 4.1), which analyzes the core reference cycle for a LBE (Lead-Bismuth-Eutectic) cooled core coupled with a LBE windowless target. Here the neutron source, defined as the first neutrons appearing in the system with energy under 20MeV, is analyzed energetically and spatially by means of the Monte Carlo computer code MCNPX 2.5.b. These results afe needed for the ERANOS code for burn-up calculations
Fission Fragment Production from Uranium Carbide Disc Targets.
No full textIl rapporto propone per la diffusione interna un lavoro realizzato in collaborazione con INFN-LNL da S. Cevolani, C. Petrovich e A. Andrighetto (INFN) pubblicato su: The European Physical Journal A DOI 10.1140/epja/i2005-10064-
Comparing energy scenarios by means of ternary diagrams
No full textThe use of ternary diagrams is here proposed as a straightforward means to show the relation between the electricity generating mixes and relevant scenario parameters, such as system carbon emissions (gCO2/kWh) and generation costs (c€/kWh). The effectiveness of the representation is improved by plotting contour lines inside the diagram to help the reader to identify the generation mixes that meet specific economic and environmental requirements. Along with the description of the potentiality of the ternary diagrams in the energy scenario field, an explanatory application is also reported. It demonstrates the helpfulness of the graph in performing preliminary assessments of specific energy policies. The levelized cost of electricity (LCOE) of a future (2030) Italian electricity generation system largely based on renewables - providing 50% of the demand - is plotted in a ternary diagram as function of the combination of different renewable electricity generation shares. The graph clearly shows that the cheapest electricity can be achieved by an electricity generation mix that covers 20-30% of the electricity demand with wind power, 0-20% with photovoltaic (PV) and 10-30% with the other renewables. Further assessments demonstrate that the PV capacity should be limited so as to reduce the installation of expensive energy storage capacity while wind power along with electricity from biomass could effectively contribute in reducing the system LCOE.. © FrancoAngeli
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